Solvent can interact with the biological macromolecules in two ways. It can bind to the solute strongly and specifically, giving rise to, among other things, the hydration force. With V. A. Parsegian and D. Rau, we measured the magnitude of this force between DNA double helices. This aspect of the study is reported by Parsegian. In addition, we compared the protein-protein interactions that occur in the crystal with those between the subunits in multimeric protein complexes. We found that the former is generally more complex than the latter but few other generalizations were possible. This aspect of the study will continue. The solvent can also influence the behavior of macromolecules in a general and non-specific way. Study of this aspect generally coincides with the study of the hydrophobic phenomenon. This was studied using statistical mechanical methods. I have succeeded, for example, in finding the physical origin of the hydrophobic volume shrinkage phenomenon and in computing the extent of volume fluctuation of globular protein molecules. However, in order to properly apply this rigorous procedure to biological macromolecules, a way must be found that will handle nonspherical solutes. A new approximation scheme was discovered to this end and future efforts will be concentrated on developing this approximation scheme.